To control fluid flows, servo valves that are controlled by a pilot valve are frequently used. Such a valve arrangement can be found, for example, in DE 100 06 600 B4. This valve arrangement has a main valve with a valve closure element associated with a valve seat. A spring clamps the valve closure element against the valve seat. To open this main valve, a fluid-actuated drive device in the form of a diaphragm is used. The fluid-actuated drive device is located in a housing element and connected with the valve closure element via a valve rod. For the controlled and guided pressure action of the diaphragm and the generation of a force that opens the main valve, an electromagnetic pilot valve is provided that is designed as a switch valve. It connects either the two chambers, divided by the diaphragm in the housing, with one another, or in its other switch position, it connects one of the chambers with the discharge side of the valve. In this way, it is possible to open or close the valve arrangement with small electrical outputs. To keep the valve arrangement open, however, the electromagnet of the pilot valve must be constantly supplied with current. Even if a holding current reduction is effected, this leads to non-negligible power consumption. This cannot be reduced arbitrarily either. For safety reasons, the pilot valve must switch into the position required for bringing the valve arrangement safely to the closed position if there is a power failure. To this end, a corresponding restoring spring is required that can reliably overcome all residual forces that can appear in a magnetic circuit. The holding current of the pilot valve must be dimensioned correspondingly large, so as to overcome, in turn, the closure spring in the operated state.
An on/off valve with intermediate values cannot be adjusted over the long term. Moreover, such a valve arrangement does not permit any modulation of the gas flow. If gas devices with varying power consumption are to be controlled by such a valve, additional modulation valves are required.
On the basis of this, the objective of the invention is to create an improved valve arrangement that improves on the aforementioned valve arrangement in at least one respect.
This objective is attained by the valve arrangement in accordance with the invention, and also by the valve control method in accordance with the invention.